1. Field of the Invention
The present invention relates generally to an ultrasonic welding apparatus; and, more specifically, to a replaceable sonotrode tip for use with an ultrasonic welding apparatus.
2. Description of Related Art
Ultrasonic welding of various materials is known. The process involves vibrating overlapping workpieces clamped between a sonotrode and an anvil. Frictional forces occurring between the vibrating workpieces create a bond or weld that occurs at the interface between the workpieces, effectively joining them to one another. Various sonotrode and anvil surface configurations; i.e., the surface that contacts the workpieces, are known and used to transfer energy from the sonotrode to the interface between the workpieces.
During the course of welding operations, the sonotrode will wear slowly. It is also possible that some of the weldment material may build up on the sonotrode, potentially clogging the gripping or contact surface of the sonotrode, and reduce the efficiency of the ultrasonic welding apparatus as energy normally transferred to the workpiece to perform the weld is lost. The more clogged or worn the gripping or contact surface of the sonotrode, the more its efficiency is reduced. Ultimately, it becomes necessary to clean or replace the sonotrode.
In some instances, it may be advantageous or necessary to change the sonotrode depending upon the material being joined. For example, welding different materials may require different sonotrodes or more specifically, different gripping patterns on the contact surface of the sonotrode.
Sonotrodes are typically manufactured by machining a block of raw stock, typically tool steel, into a predetermined shape. The machining process usually includes machining a taper on one end of the sonotrode such that it fits in a corresponding tapered aperture located in the end of a reed of the ultrasonic welding apparatus. A sonotrode typically includes a plurality of threads cut into the outer circumferential surface thereof. The threads operate in conjunction with a threaded fastener, such as a nut, to extract or remove the sonotrode from the reed. Specifically, rotating the threaded fastener on the threads of the sonotrode causes the threaded fastener to engage the lower surface of the reed and correspondingly extract the sonotrode by pulling the sonotrode from the reed.
As indicated above, currently sonotrodes are manufactured by starting with a block of raw stock, much of which is machined away to create the sonotrode. The raw stock, typically high-grade tool steel, is expensive. At the start, the block of raw stock must be of a size or diameter greater than the outer diameter of the threads cut or machined into the outer circumferential surface of the sonotrode, as the threaded portion or threads in the outer circumferential surface of the sonotrode are formed by removing material from the block of raw stock. In addition, additional material must be machined away to taper one end of the sonotrode, such that it mates with a corresponding taper in the reed of the ultrasonic welding apparatus.
Besides being costly from a material standpoint, i.e., much of the raw stock is removed and discarded during the machining process; the machining process is labor intensive, which also increases sonotrode costs. Finally, the pattern on the gripping or contact surface of the sonotrode often requires placement in a precise position or orientation with respect to the direction of reed vibration.
A clogged or worn sonotrode must be cleaned or replaced. In either case, the sonotrode is removed from the reed. Thus, there is a need in the art for an ultrasonic welding tool whereby a clogged or worn sonotrode can easily be removed from the reed and replaced with a clean sonotrode in a quick and efficient manner to reduce downtime and correspondingly maintain continued operation of the ultrasonic welding equipment. Further, since it may not be feasible to clean the contact surface of the sonotrode, there is a need for a sonotrode that requires less machining or fabrication time to produce a finished sonotrode which correspondingly reduces the overall cost or expense of the sonotrode.